Electronically controlled throttle valve with limp home mechanism

Abstract

The subject invention is a linkage assembly for an electronically controlled throttle (ETC) that provides for the precise setting of a limp home engine speed for a vehicle. Essentially a controlled amount of movement is attained between a closed position and a limp home throttle position. A throttle valve is attached to a first shaft and rotates to regulate air intake. The first shaft is attached to a sector gear. The sector gear is driven by the ETC. A stop bracket limits the amount that the sector gear can close the throttle valve. The stop bracket defines an opening, and a cam is disposed within the opening. A spring biases the stop bracket against the cam. Normally, the ETC can overcome the spring and the stop bracket is forced against the cam such that stop bracket contacts the cam to define a closed throttle position. Of course, when operational the ETC can drive the valve to open position as demanded by the vehicle. The limp home engine speed is set by a preset by the difference between the length of the opening of the stop bracket and a width of the cam. If the ETC becomes disabled, there is not enough force to overcome the spring and move the sector gear to the closed throttle position, instead the sector gear remains at the second stop position to provide the limp home engine idle speed that allows a driver to sufficiently maneuver the vehicle.

What is claimed is:  
     
       1. An electronically controlled throttle valve assembly for a motor vehicle comprising; 
       a throttle body defining an air flow passage;  
       a throttle valve for regulating air through said air flow passage movable between an open position and a closed position, said throttle valve having first and second areas and said first area is greater than said second area;  
       a shaft fixed to rotate said throttle valve about an axis;  
       said first and second areas arranged on opposite sides of said axis and the intake of air causes a pressure force on said first and second areas such that said throttle valve is rotated about said axis towards said closed position.  
     
     
       2. The assembly of  claim 1 , wherein said throttle valve includes an airfoil shape, such that the intake of air causes a lift force to rotate said throttle valve towards said closed position. 
     
     
       3. The assembly of  claim 1 , further including a first biasing member attached to said shaft, said first biasing member engaged when said throttle valve is in said fully open position to bias said throttle valve towards a closed position. 
     
     
       4. The assembly as in  claim 3 , wherein said first biasing member is a linear plastic rod extending from said shaft such that in said open position said plastic rod provides a biasing force towards said closed position. 
     
     
       5. The assembly of  claim 1 , further including a lever attached to rotate said shaft and a second biasing member attached to said lever, said second biasing member engaged when said throttle valve is in said closed position to bias said throttle valve towards said filly open position. 
     
     
       6. The assembly as in  claim 5 , further including an electric motor to drive said lever to rotate said shaft and said throttle valve between said open and closed positions. 
     
     
       7. The assembly as in  claim 6 , wherein said second biasing member biases said throttle valve toward said fully open position to a limp home throttle valve position, and said limp home throttle valve position is attained when said electric motor is disabled and cannot overcome said second biasing member. 
     
     
       8. The assembly as in  claim 5 , wherein said second biasing member is a circular plastic spring. 
     
     
       9. An electronically controlled throttle valve assembly for a motor vehicle comprising; 
       a throttle body defining an air flow passage;  
       a throttle valve having an airfoil shape for regulating intake of air movable between an open and closed position;  
       a shaft fixed to rotate said throttle valve about an axis;  
       said airfoil shape of said throttle valve creating a lift force to rotate said throttle valve about said axis towards said closed position.  
     
     
       10. The assembly of  claim 9 , wherein said throttle valve includes first and second areas and said first area is greater than said second area, said first and second areas arranged on opposite sides of said axis and the intake of air causes a pressure force on each of said areas such that said throttle valve is rotated towards a closed position. 
     
     
       11. The assembly of  claim 10 , further including a first biasing member engaged when said throttle valve in said fully open position and biases said throttle valve toward said closed position. 
     
     
       12. The assembly of  claim 10 , further including a lever attached to rotate said shaft, and a second biasing member attached to said lever, said biasing member engaged when said throttle valve is in said closed position to bias said throttle valve toward said open position to a limp home position such that the engine provides sufficient power to maneuver the motor vehicle. 
     
     
       13. The assembly of  claim 12 , further including a drive to rotate said lever between said open and closed positions. 
     
     
       14. The assembly of  claim 13 , wherein said second biasing member is a circular spring, said circular spring biases said throttle valve from said closed position to said limp home position upon disablement of said drive.